Optical waveguides had a profound impact on modern telecommunications, but are increasingly being used for other applications as well. For example, fiber-based endoscopy systems are used in medicine to view remote locations within the body. Advantages of optical fibers are that they can guide light over significant distances with low loss, they are flexible, they are very thin, they have a low cost, and they are made of inert, non-toxic materials.
Optical waveguides can be classified according to the transverse modes of propagation they support. A mode can be seen as a spatial configuration of light that is allowed to propagate within the waveguide. Single-mode waveguides have only one mode, meaning that light can only be guided through the waveguide with one predefined spatial distribution. In single-mode waveguides, information can only be transmitted modulating the light signal in time, and it is not possible to directly transmit spatial information such as images, because the spatial shape of light is fixed.
Multimode waveguides on the other hand support multiple transverse modes, meaning that the light can be guided with a variety of spatial configurations. Each mode has different propagation characteristics within the waveguide, because of modal dispersion and modal mixing. As a consequence, the spatial configuration of the light at the input of the waveguide is not maintained until the output. However, if the propagation characteristics of each mode within the waveguide are known by either measurement or calculation, it is possible to transmit spatial information such as images.
One problem in multimode waveguide imaging systems is caused when the waveguide is subject to bending. As a consequence, the propagation characteristics of the multiple modes change relatively to each other depending on the geometrical configuration of the waveguide. While the characteristics can be calculated or measured in advance for one particular bending state of the waveguide, the same data is not valid for other bending states. This limits the flexibility of multimode waveguides as imaging devices, e.g. in the context of endoscopy.
U.S. Pat. No. 5,956,447 proposes to divide the waveguide in two parts, a pre-bent auxiliary part, and a work part. The work part can be used for flexible imaging. Bends incurred in the work part of the waveguide can be compensated by loosening the pre-bending of the auxiliary part. However, in practice, it can be difficult to precisely compensate bending in a freely moving waveguide. The required compensations must be found by trial and error, and a very involved mechanical system would be needed to compensate all the integrals of curvature completely.
Accordingly, in light of the above discussed deficiencies of the background art, there is a strong need to provide for systems, devices and methods to improve existing solutions to compensate for bending that is applied to a waveguide.